This application relates generally to the field of structural, non-linear, arched beams (referred to herein as arches), and more particularly to such arches which are composite arches comprising a tension member or both compression and tension members.
Structural arches have been in use for thousands of years. Early arches were masonry arches and therefore very heavy and requiring extensive foundation support. The load placed on the arch translated from a vertical force to a horizontal outward force at each arch end, such that it was necessary to provide buttresses or similar structural members to counter these forces. As new materials were developed, such as for example steel and other metals, arch designs that were hybrids or composites evolved. One early type of arch known as a Whipple arch is a tied or bowstring arch, wherein a tension member, such as a metal bar (“the string”), is affixed between the ends of the arch (the “bow”) to resist the outward force. Most recently, arch structures incorporate modern synthetic materials having high strength properties, such as for example carbon-fiber reinforced polymers (CFRP) or glass-fiber reinforced polymers (GRFP). While incorporation of these materials may result in a reduction of weight, it has been difficult to balance the utilization of the new materials with the structural requirements of the arch, especially for arches of significant length.
Examples of hybrid arches or beams are shown in U.S. Pat. Nos. 6,145,270 and 7,562,499 to Hillman and in U.S. Pat. Nos. 7,895,799 and 8,141,307 to Hillman and Zicko. Hillman/Zicko show arches or beams wherein tension members in the form of steel rebar are positioned along the bottom of an elongated box member formed of a GRFP, the box having a rigid foam support and several concrete layers. These arches or beams are still very heavy due to the large amount of concrete present in the arch or beam.
It is an object of this invention to provide a structural arch that is significantly lighter and smaller in cross-section than traditional arches, yet still provides excellent strength properties. It is a further object of this invention to provide such arches wherein an elongated tension member and/or compression member is contained within the arch body itself.